The present invention relates to a digital wireless communication system. Such a system can be a cellular or other wireless communication system including wireless communication stations such as mobile radio handsets, combined mobile radio data processing devices, cordless telephones, or any other suitable wireless telephone device. The system can be any frame oriented system suitable for conveying speech data, control data, and user data.
From the handbook xe2x80x9cSpeech and Audio Coding for Wireless and Network Applicationsxe2x80x9d, B. S. Atal et al., Kluwer Academic Publishers, 1993, pp. 85-92, a variable speech or adaptive rate coder is known for use in a digital cellular telephone system. From speech signal samples, the speech coder generates speech coder data which are typically contained in 20 ms frames. Periods of silence in the speech signal and background noise are coded at a lower rate so that system capacity is increased. For signaling data to be sent, the system can instruct the speech coder to encode the speech at half rate for one or two frames, allowing the remaining bits which would have been used for full rate speech data instead. Because speech is only coded at half rate for 20-40 ms, speech quality is not significantly degraded, though the amount of signaling data that can be conveyed without causing degrading of speech quality is limited.
The proposed TIA/EIA/IS-707 Standard defines data service options for wideband spread-spectrum systems. At a Rate Set 1, at full rate operation of a speech coder in the system, so-called Primary Traffic is conveyed in bits/frame. At a lower rate of the speech coder, the frame may contain signaling traffic bits or so-called Secondary Traffic bits. The signaling bits are to be considered as in-band data and the Secondary Traffic can consist of user data. Particularly when there is a desire to simultaneously convey speech data and a moderate amount of user data, the speech quality is substantially degraded. This is due to the fact that the speech coder is then forced to operate at a lower rate for a great number of speech frames, i.e., not only for frames containing silent speech periods and/or background noise information but also for speech frames carrying meaningful speech data. Typical applications today in which considerable amounts of data have to be conveyed, either uni-directional or bidirectional, are Internet applications, or the like. In this respect, there is a trend to couple or integrate cellular phones with data devices or personal computers.
Thus, what is needed is a mechanism of simultaneously conveying speech data and substantial amounts of user data without substantially degrading speech quality.
It is an object of the invention to provide a digital wireless communication system simultaneously conveying high quality speech signal data and optimal rate dedicated user data.
It is another object of the invention to further optimise the throughput of the dedicated user data in the event speech signal data can be transmitted without substantial decrease of speech quality.
It is yet another object of the invention to also simultaneously exchange signaling data.
It is yet another object of the invention to flexibly adjust the type of data to be exchanged between the wireless communication infrastructure network and the wireless communication stations.
It is yet another object of the invention that the system can independently act upon speech data and dedicated user data, preferably using different protocols for speech data and dedicated user data, preferably applying a protocol most suitable for processing dedicated user data.
It is yet another object of the invention to make available a means for exchanging data which is optimal when data traffic is extended over a long period but is irregular.
In accordance with the invention, a digital wireless communication system is provided which comprisies a wireless communication infrastructure network and a plurality of wireless communication stations configured for wireless communication with the wireless communication infrastructure network, the communication using an air-interface protocol for exchanging data in frames, which frames are constituted for simultaneously comprising speech data generated at a full rate by a speech coder and dedicated user data generated by a user data application .
A great advantage is that it always can be guaranteed that the speech coder can operate at full rate on meaningful speech signal samples so that speech quality is not degraded, while at the same time dedicated user data can continuously and uninterruptedly be conveyed. On a frame-by-frame basis, the rate of the speech coder can be adapted so that maximum throughput can be achieved in conveying the dedicated user data. Preferably having a dedicated user data channel independent of the speech data channel on the same air-interface frame provides low cost simultaneous voice and data services.
Preferably, data throughput of dedicated user data is increased at instances where speech data can be transmitted at a lower rate without loss of speech quality. Preferably, speech and dedicated user data are independently routed and processed by the system. Further embodiments are discussed hereinafter.
The invention can advantageously be used for Internet applications, or the like. Another very advantageous application is conveying dedicated user data while using a bi-directional data link that is open for a long period of time. Herewith, applications such as interactive paging and web-chatting, or even simultaneous exchange of still picture data with high quality cellular voice data link, can be easily implemented because the data link is open all the time and can be used at choice, i.e. for data transmission of dedicated user data system resources are only used when needed. Another great advantage is that the user data link does not interfere with usual signaling or control in the cellular system, i.e. cellular system control is not made more complex as compared to existing systems.